Longitudinally oriented felts have heretofore been made by a number of different processes employing different types of apparatus. In one case, hereinafter referred to as a "full width needling process" and illustrated and described in Canadian Patent No. 980,556 to Cedercreutz, a strip of felting batt is pressure-rolled onto a fabric base in a plurality of longitudinally extending spiral windings until it is fully wound on to the base fabric and, thereafter, the spirally wound longitudinally oriented felt is needled together. The apparatus employed in the Cedercreutz patent utilizes a single, full width, needling mechanism. The adhesion which can be achieved between the loops of felting batt and the underlying base fabric due to the contact pressure generated by the pressure roller is, in the absence of any preliminary needling, insufficient to prevent the felting batt from locally lifting away from the base fabric, so that wrinkles form during the subsequent needling operation. Another disadvantage of the foregoing full width needling process and apparatus is that the joints between loops of the felting batt tend to separate, allowing the loops to shift transversly relative to one another and resulting in variations of thickness in the transverse direction of the completed, needled, longitudinally oriented paper machine felt.
One attempt to overcome the disadvantages inherent in the full width needling process is illustrated and described in U.S. Pat. No. 4,536,927 to Feyerl et al. In the Feyerl et al patent, a needling mechanism having a working width corresponding to the desired width of the completed, needled, longitudinally oriented paper machine felt is utilized in conjunction with a felting batt strip feeder which is transversely reciprocable throughout the working width of the needling mechanism. A small needling unit, having a working width corresponding to that of the felting batt strip, is provided between the feeder and the needling mechanism. The small needling unit is transversely reciprocated in unison with the feeder throughout the working width of the larger needling mechanism. The small needling unit needles each loop of the felting batt strip to the base fabric at the time that the felting batt strip is applied to the base fabric to keep the loops in place. Thereafter, when the felting batt strip has been wound into a number of needled loops corresponding to the full width of the composite longitudinally oriented paper machine felt, the full width needling mechanism is activated to needle the composite construction. The foregoing process, hereinafter referred to as the "sequential strip and full width needling process" represents an improvement over the use only of a full width needling process for needling longitudinally oriented felts. However, the apparatus employed in such sequential strip and full width needling process requires that a bulky needling unit be traversed across the full width of the machine in concert with the felting strip batt web, resulting in problems relating to adequately supporting and transversely reciprocating the needling unit, as well as problems relating to driving the needles of the transversely reciprocating needling unit.
For the foregoing reasons, prior forms of apparatus for manufacturing endless, needled, longitudinally oriented paper machine felts, either by the full width needling process or by the sequential strip and full width needling process, have not been entirely successful in practice.
It is, therefore, a primary object of the present invention to provide an improved apparatus for manufacturing endless, needled, longitudinally oriented paper machine felts by the sequential strip and full width needling process.
Another object of the present invention is to provide improved apparatus for manufacturing endless, needled, longitudinally oriented paper machine felts, in which a full width needling mechanism having a plurality of smaller, selectively operable needling units therein is employed to needle the felting batt strip to adjacent felting batt loops and to the base fabric (where one is used) as the strip is applied thereto.
A further object of the present invention is to provide an improved apparatus for manufacturing endless, needled, longitudinally oriented paper machine felts in which a second full width needling mechanism, having a plurality of selectively actuable smaller width needling units therein, is positioned between a transversely reciprocating roll of felting batt strip and a first full width needling mechanism, and the needling units are selectively actuated to needle the felting batt strip to the adjacent felting batt loops and to the base fabric (where one is used) only while the strip is passing under a corresponding needling unit while it is being wound into loops.
Additional objects and advantages of this invention will become apparent as the following description proceeds.